The Most Important Applied Research Paper This Year? Perhaps Any Year?

Walk through a poor rural or urban landscape and the vista seems to repeat itself unchanged. But delve deeper and differences appear. One robust finding from India is that poor Muslim children have a much better survival rate than poor Hindu children – childhood mortality is about one-fifth lower among Muslims. This finding is unaltered by adjusting for known confounders and, in any case, Muslim children in India are poorer and less educated than their Hindu peers. In development circles this is known as the “Muslim mortality paradox”. It was solved by Geruso and Spears in July this year [1] in a brilliant study based on the USAID Demographic Health Survey. Muslims are much less likely to defecate in the open than are Hindus. Hindus often regard defecation in the home as unclean and are more likely than Muslims to go outside to relieve themselves, even if the house is equipped with a functioning lavatory. The study shows a significant correlation between defecation in the open and mortality and confirms what has been thought by many politicians, right back to Mahatma Gandhi, who said “Sanitation is more important than independence”. I believe that we can draw a cause and effect inference from this data because:

  • It withstands adjustment for sex, mother’s education and wealth, and mother’s age at birth. In fact, controlling for education and wealth widens the gap in mortality between religions.
  • Muslims are no more likely to wash their hands, use soap or filter water than Hindus, and are less likely to have access to running water according to the data; again a bias against the hypothesis.
  • It has a good biological explanation. Chronic/recurrent infection/infestation causes stunting due to enteropathy [2] and perhaps a persistently altered microbiome.
  • The increased risk among Hindus who use a lavatory declines in proportion to the proportion of surrounding people who also use a lavatory.
  • Breastfed Hindu children experience much smaller increases in risk than non-breastfed Hindu peers – to me this was ‘the clincher’.

The effect of poor sanitation is so large, that it accounts for a greater quantum of mortality than the difference between the richest and poorest 20% of the population. The findings make the case for improved sanitation in all poor rural and urban areas of the world. In a previous blog I discussed failed approaches to improved health in slums – slum clearance just moves the problem elsewhere; land tenures creates slum-lords, etc. Behaviour change and other methods to improve sanitation could be the big breakthrough in improving lives of slum dwellers and rural poor people alike. CLAHRC Africa is already conducing a pilot study in West Africa, led by Dr Semira Manaseki-Holland, and we are aware of only three cluster intervention trials, all of which are use of solar-powered disinfection of drinking water.[3] [4] [5] However, the USAID Water, Sanitation and Hygiene (WASH) programme is co-ordinating further studies. We think that the step wedge design [6] is particularly suitable for evaluation in such interventions and they should include sound economic and educational end-points, along with health measures.

— Richard Lilford, CLAHRC WM Director


  1. Geruso M, & Spears D. Sanitation and health externalities: Resolving the Muslim mortality paradox. 2014. Working paper, University of Texas, Austin.
  2. Spears D, Ghosh A, Cumming O. Open Defecation and Childhood Stunting in India: An Ecological Analysis of New Data from 112 Districts. PLoS One. 2013. 8(9): e73784.
  3. du Preez M, McGuigan KG, Conroy RM. Solar Disinfection of Drinking Water In the Prevention of Dysentery in South African Children Aged under 5 Years: The Role of Participant Motivation. Environ Sci Technol. 2010; 44(2): 8744-9.
  4. du Preez M, Conroy RM, Ligondo S, et al. Randomized Intervention Study of Solar Disinfection of Drinking Water in the Prevention of Dysentery in Kenyan Children Aged under 5 Years. Environ Sci Technol. 2011; 45(21): 9315-23.
  5. McGuigan KG, Samaiyar P, du Preez M, Conroy RM. High Compliance Randomized Controlled Field Trial of Solar Disinfection of Drinking Water and Its Impact on Childhood Diarrhea in Rural Cambodia. Environ Sci Technol. 2011; 45(18): 7862-7.
  6. Hemming K, Lilford RJ, Girling AJ. Stepped-wedge cluster randomised controlled trials: a generic framework including parallel and multiple level designs. Stat Med. 2014

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